The invention relates to the termination of insulated electrical conductor wires to a printed circuit board, and more particularly to the provision of a crimp contact and method for terminating the printed circuit board.
A printed circuit board may consist of multiple layers of electrical circuitry built up on one another. Plated-through holes are formed in the printed circuit board to interconnect the various levels of electrical circuitry. Insulated electrical wires are terminated in the plated-through hole to make electrical connection with the printed circuit board.
Normally, the conductor wires have been terminated by stripping the insulation from the ends of the wire, inserting the bare wire strand into the plated-through hole and soldering the wire in the hole. This involves a large number of plated-through holes and a large number of individual wires which must be stripped and soldered individually in the hole.
The quality standards for terminated printed circuit board in the military and commercial markets are extremely high. It is very difficult to solder a discrete wire to a printed circuit board without a number of problems occurring. First, there must be a proper insulation gap between the wire and the board. The tinining of the wire strand in preparation for soldering is also very difficult and time consuming. Each step has to be inspected. Bird caging is also a problem when manipulating the wire strand after tinining into the hole of the printed circuit board. The wire and the strands may separate resulting in a bird nest appearance. As soon as the wire strands separate, it is a cause for rejection. Once the discrete wire is properly inserted in the plated-through hole, the soldering process is very time consuming and tedious. The process requires two technicians. One technician solders while the other operator holds the wire at the plated-through hole with the proper insulation gap. The technician then solders the wire in the hole from the opposite side. This process is very slow for mass production of printed circuit boards having a large number of plated through holes.
Often it is necessary to repair the terminated wiring at the printed circuit board. When this is done in the field, the repair process can be tedious. Hundreds of wires may be terminated at the printed circuit board with only a spacing of a few mils between the plated-through holes. In the repair process, great care must be taken not to damage adjacent wiring. In repairing the broken wire, there is a good chance that some wire length will be lost. Normally, there is not additional wire length present in order to reprocess the wire. If the wire is soldered in the plated-through hole, it is very difficult to get all of the strands out of the board without damaging the board itself. In the field, only a limited amount of tooling is available to repair the broken wire. Often the board may have to be removed and repaired in a shop.
It can be seen that the termination and repair of discrete wires at a printed circuit board involves problems to which considerable attention need to be given.
Socket contacts have been used in the electronic interconnection industry for some time in various configurations. Some of the contacts are force-fitted directly into holes in the panel or printed circuit board. Other contacts are intended to be directly inserted in through plated-through holes in similar panel or printed circuit boards. The considerations involved with each type of mounting are normally somewhat different. For example, U.S. Pat. No. 4,236,776 discloses an electrical socket contact having an open socket and a solder tail. The solder tail may be disposed in the opening of a plated-through hole. Ribs are formed on conical bottom surface of the socket which provides an opening between the top rim of the plated-through hole and the bottom surface of the socket contact. This facilitates flow of the solder between the space of the solder tail and the hole plating and between the hole plating and the socket contact. In the socket contact type of connector, a pin connector is normally utilized having pins which mate with the socket opening for termination. Thus, this type of connector is not suitable for terminating discrete wires through the plated holes of a printed circuit board. U.S. Pat. No. 4,080,037 likewise discloses a receptacle terminal for a printed circuit board. The terminal receptacles are placed in the holes of the printed circuit board and soldered. A pin type connector is then terminated to the board by inserting the prongs of the connector into the terminal receptacles.
U.S. Pat. No. 4,548,540 discloses an arrangement for connecting a terminal pin to a printed circuit board conductor by means of an electrically conductive elastomeric collar positioned about the terminal end and pressed into a plated-through hole in the printed circuit board. The terminal pin is then wire wrapped to terminate the individual wire to the printed circuit board. While all of the above disclosed termination arrangements which may be satisfactory for the intended application, none are entirely satisfactory for terminating and repairing a large number of discrete wires at a printed circuit board.
Accordingly, an important object is to provide a connector and method for terminating and repairing discrete wiring at a printed circuit board.
Another object of the invention is to provide a method for terminating and repairing printed circuit boards which uses a unique crimp contact.
Another object of the invention is to provide a crimp contact for terminating a printed circuit board wherein a discrete wire may be crimped and the contact then firmly seated in a plated-through hole in a printed circuit board for reliable and positive electrical connection between the plating and the crimp contact.
Another object of the invention is to provide a crimp contact and method for terminating a printed circuit board wherein the crimp contact is supported above the plating or the hole in which it is seated with adequate clearance between the solder post and bottom of the contact so that a complete and even distribution of solder occurs.
Another object of the invention is to provide a crimp contact for terminating a printed circuit board and method wherein the contact may be crimped to a wire and seated in the plated-through hole of the printed circuit board in a manner that the flow of solder is complete upwardly along the solder post of the contact to the top and between the plating and contact.
Another object of the invention is to provide a method of terminating a printed circuit board wherein large numbers of discrete wires may be prepared and crimped into PG,7 individual crimp contacts which are inserted and seated firmly in a plated-through hole of the printed circuit board wherein the contacts may be firmly seated in the plated-through holes and soldered in large numbers for mass production.
Still another object of the invention is to provide a crimp contact and method for repairing a printed circuit board wherein the crimped contact may be easily removed from the printed circuit board for repairing broken wiring.